Adding GFIC protection for old two-wire system


Old 01-07-08, 11:21 AM
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Adding GFIC protection for old two-wire system

60 year old house is wired with just two wire; that is, no ground wire running through the junction boxes. An electrician has suggested re-wiring the circuits to add ground wire and also, to the extent any of the old circuits are retained, to replace the old receptacles with GFIC outlets. I have several questions on this: What is gained in terms of safety by adding the GFI outlets? Also, what is connected to the green ground screw since the circuit has no ground wire? Finally, is installation of GFI circuit breaker at the panel for these circuits an alternative to adding GFI at each outlet? If so, which approach would you recommend? Thanks.
Old 01-07-08, 11:29 AM
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The only thing gained by the GFCI is the third hole. If you have devices that have three prong plugs you will be able to plug them in. They won't be grounded but they will be protected by GFCI which is about as safe. There will nothing connected to the ground screw on the GFCI receptacles.
A GFCI breaker is an option however it is more expensive than adding a GFCI as the first device on the circuit and then using the LOAD terminal to feed the remainder of the circuit.
Some three prong devices like surge suppressors should have a real ground and the GFCI is not viable option for them.
If you have no need to plug in three prong devices in the ungrounded receptacles then leave them as two prong.
Old 01-07-08, 11:36 AM
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Old 01-07-08, 11:45 AM
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joed has covered it.

Adding GFCI protection allows you to use receptacles that have a hole for the ground prong of a three wire cord. However, no ground is provided.

An appliance that needs a ground for safety (for example a refrigerator) is safest in a grounded receptacle. Second safest is to use an ungrounded GFCI receptacle. Third safest would be to use an ungrounded circuit without GFCI protection.

My advice is to add new circuits where you need them, and to leave the old circuits alone. If you are remodeling a complete room, then rewire that room as all new circuits.

However, I do recommend providing GFCI protection for some locations (garage, outside, kitchen, bathrooms and in the basement, if unfinished).
Old 01-07-08, 04:49 PM
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And installing downline protection, you should mark the downline outlets as GFCI Protected and No Ground.

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